Synthesis of the carbanion 1,1,2-tricyano-2-(3,4-dicyano-5-imino-2,5

ABSTRACT

A process is described for preparing the carbanion of the title as its sodium salt with quantitative yields and at a high level of purity, by a two-stage reaction between disodium-tetracyano-ethylene, Lewis acids and water. Metal complexes, prepared from said carbanion, are particularly suited for methods of using the metal complexes as dyes in industrial applications.

This is a division of application Ser. No. 07/627,576 filed Dec. 14,1990.

PRIOR ART

The carbanion1,1,2-tricyano-2-(3,4-dicyano-5-imino-2,5-dihydro-1H-pyrrol-2-ylidene)ethanide, of formula: ##STR1## which for simplicity is identifiedhereinafter as "pyrroliminocyanin", was prepared for the first time asthe tetraphenylarsonium salt (As Ph₄)C₁₁ N₇ H₂ : see Angew. Chem. Int.Ed. Engl. 24 (1985) 426.

It was subsequently found that this anion when in the presence of abivalent metal ion isomerizes to givebis-(1,2,6,7-tetracyano-3,5-diimino-3,5-dihydro-pyrrolyzinido) metal, offormula: ##STR2## see Angew. Chem. Int. Ed. Engl. 28 (1989) 1049, whichdescribes the crystalline structure of the copper complex ofpyrroliminocyanin, Cu(C₁₁ N₇ H₂)₂. The same publication also describesthe synthesis of the bivalent zinc, iron and nickel complex analogues.As in the case of the copper complex, these are centre-symmetricalplanar metal complexes.

All these complexes are analogues both to the metal acetyl-acetonates,given the method of coordination of the ligand chelating monoanion of βtype), and to tetracyanoquinodimethane, given the high substitution withcyano groups. For these reasons these complexes are importantcoordination compounds, useful in the synthesis of molecular materialsand in heterogeneous catalysis.

The synthesis of pyrroliminocyanin, described in Angew. Chem. Int. Ed.Engl. 24 (1985) 426, has various drawbacks. Tetracyano-ethylene (C₆ N₄)is reacted with titanium tris-bipyridyl, which is a pyrophoric substanceand therefore difficult to handle. The intermediate complextitanium-bis-bipyridyl-tetracyanoethylene is acidified to separate thedesired product int he form of the tetraphenylarsonium salt. The yieldis low, about 40%, and column chromatography must be used to obtain aproduct with an acceptable degree of purity able to give the aforesaidmetal complexes.

SUMMARY OF THE INVENTION

A process comprising the condensation of disodium-tetracyano-ethylene inthe presence of certain Lewis acids has now been found which enables thesodium slat of pyrroliminocyanin to be obtained with practicallyquantitative yields. It has also been found that certain metal complexesobtained form pyrroliminocyanin are excellent dyes for industrialapplications.

DETAILED DESCRIPTION OF THE INVENTION

The condensation of the disodium-tetracyano-ethylene, which constitutesan aspect of the present invention, takes place in the presence of Lewisacids, of which the following have proved particularly suitable: silicontetrachloride, chloromethyl-silanes, zinc chloride, aluminum chloride,titanium tri- or tetrachloride, tantalum tetrachloride, niobiumpentachloride, chromium dichloride, manganese dichloride, germaniumtetrachloride, molybdenum pentachloride, tungsten hexachloride, boronfluoride complexed with ethyl ether, methyltin chlorides.

In order to identify the Lewis acid giving the best yield in promotingthe desired condensation, various tests were made on small quantities ofreagents, by the following procedure: the disodium-tetracyanoethylene(0.1 g), the solvent (tetrahydro-furan, 10 ml) and the Lewis acid (0.1g), the solvent (tetrahydro-furan, 10 ml) and the Lewis acid (0.1 g) areenclosed in a glass vial under vacuum. The vial is then heated to 80° C.for three hours under agitation. It is left to cool to ambienttemperature, then opened to the air and the contents poured into 50 mlof water. The mixture is filtered and an aqueous solution (10 ml)containing AsPh₄ Cl(0.2 g) is added to the filtrate. Thepyrroliminocyanin tetraphenylarsonium precipitates in variablequantities and purities depending on the Lewis acid.

The preferred Lewis acids are the chloromethylsilanes.

The reaction proceeds in accordance with the following overall scheme:

    4 Na.sub.2 C.sub.6 N.sub.4 +6(CH.sub.3).sub.3 SiCl+3H.sub.2 O→2 NaC.sub.11 N.sub.7 H.sub.2 +3(CH.sub.3).sub.3 SiOSi(CH.sub.3).sub.3 +6NaCl+2HCN

In reality the reaction proceeds in two stages. Int he first stage hedisodium-tetracyano-ethylene reacts with the Lewis acid in an organicsolvent chosen from ethers (preferably anhydrous tetrahydrofuran),esters (preferably ethyl acetate), aromatics (preferably toluene) andnitriles (preferably acetonitrile). In the second stage water is added.

The disodium-tetracyano-ethylene is prepared, as bis-adduct withdimethoxyethane, by the method described by Webster, Mahler and Benson,J. Am. Chem. Soc. 84 (1962) 3678. The Lewis acids, includingtrimethylchlorosilane, are commercially assailable products.

The pyrroliminocyanin sodium salt is thus obtained with practicallyquantitative yields and with sufficient purity for direct use in thesynthesis of metal complexes.

It has also been found, and constitutes a further aspect of the presentinvention, that metal complexes obtainable form the pyrroliminocyaninsodium slat by reaction with metal halides in an aqueous-etherenvironment, are useful as dyes for plastic materials and fibres.

In this respect, the metalation of the pyrroliminocyanin induces abathochromic shift of 120 nm and an increase int he absorptioncoefficient of about 4 times.

The following examples are given as non-limiting illustration of theinvention.

EXAMPLE 1 Preparation of Pyrroliminocyanin Sodium Salt

2.94 g of the bis-adduct of Na₂ C₆ N₄ with dimethoxyethane are placed in90 ml of freshly distilled, deoxygenated anhydrous tetrahydrofuran. 1.81g of (CH₃)₃ SiCl are added to this solution, operating in a nitrogenatmosphere. The solution becomes intensely coloured firstly red and thenviolet. It is stirred at ambient temperature for 1 hour, then heatedunder reflux for 3 hours. NaCl precipitates on cooling to ambienttemperature. The solvent and excess (CH₃)₃ SiCl are eliminated byevaporation under vacuum. The residue is taken up in acetone and theNaCl filtered off. At this point the precaution of operating undernitrogen is no longer necessary. 10 ml of water are added to the violetacetone solution and the water and hexamethyldisiloxane are evaporatedunder vacuum to obtain a dark green microcrystalline solid ofcomposition NaC₁₁ N₇ H₂.2H₂ O with a quantitative yield and sufficientpurity for direct use in the synthesis of meal complexes.

If, after cooling to ambient temperature in the aforesaid procedure, 100ml of an aqueous solution containing 1.75 g of tetraphenylarsoniumchloride As(C₆ H₅)₄ Cl are added to the violet tetrahydrofuran solution,after evaporation in air until the solution is decolorized, a goldenmicrocrystalline precipitate is obtained, which is filtered off andrecrystallized from 1:1 acetone/water by slow evaporation in air. Inthis manner 2.18 g of As(C₆ H₅)₄ C₁₁ N₇ H₂ are obtained with I.R and U.Vspectroscopic properties identical to those of the product described inAngew. Chem. Int. Ed. Engl. 24 (1985) 426.

EXAMPLE 2 Preparation of the copper complex of pyrroliminocyanin

2 of NaC₁₁ N₇ H₂.2H₂ O prepared in accordance with Example 1 aredissolved in 50 ml of tetrahydrofuran. 100 ml of an aqueous solutioncontaining 7 g of CuCl₂.2H₂ O are added to the violet solution. Thecolour of the solution changes immediately from violet to blue. Theaqueous solution is allowed to evaporate in air, and when it has reducedto one half its initial volume 2; 5 g of Cu(C₁₁ N₇ H₂)₂.2THFprecipitate, this having spectroscopic properties identical to those ofthe product 4c, the structure of which was resolved with X-rays, asdescribed in Angew. Chem. Int. Ed. Engl. 28 (1989) 19050.

The bivalent complexes of nickel and cobalt are prepared in like manner.

Zinc, manganese and iron complexes are also prepared in like manner,however it is necessary to operate in an anhydrous environment(anhydrous tetrahydrofuran under nitrogen), using the respectiveanhydrous metal dichlorides as stating materials. In this case, it isalso necessary to recrystallize the reaction products to separate themfrom the sodium chloride.

We claim:
 1. A method for using metal complexes, ofbis-(1,2,6,7-tetracyano-3,5-diimino-3,5-dihydro-pyrrolyzinide)comprising preparing said metal complex by reacting a sodium slat of1,1,2-tricyano-2-(3,4-dicyano-5-imino-2,5-dihydro-1H-pyrrol-2-ylidene)ethanide with bivalent metal halides and applying said metal complexesas dyes to plastic materials or fibers.
 2. A method of dyeing plasticmaterials or fibers comprising preparing a metal complex having ageneral formula: ##STR3## and applying said metal complex to the plasticmaterials or fibers.